[vmbase] Change payload_range in MemoryTracker to Option

As this parameter is needed in pvmfw but not in rialto.

Bug: 284462758
Test: m pvmfw_img
Change-Id: Iaed98a7f4a7d4e98b2fc59e9de8e277608a9a5e2
diff --git a/pvmfw/src/entry.rs b/pvmfw/src/entry.rs
index a4b8a64..fc96e53 100644
--- a/pvmfw/src/entry.rs
+++ b/pvmfw/src/entry.rs
@@ -229,7 +229,7 @@
         page_table,
         crosvm::MEM_START..memory::MAX_ADDR,
         crosvm::MMIO_START..crosvm::MMIO_END,
-        memory::appended_payload_range(),
+        Some(memory::appended_payload_range()),
     ));
 
     let slices = MemorySlices::new(fdt, payload, payload_size)?;